Mixed-signal semiconductor components are integrated electrical circuits which process both digital and analog signals. A typical test apparatus for mixed-signal semiconductor components contains a loadboard for holding the semiconductor component which is to be tested. Electrical lines on the loadboard connect the semiconductor component to be tested to a tester. The tester actuates the semiconductor component in order to check its functionality. In addition, the test apparatus has a measuring apparatus which evaluates the output signals from the semiconductor component. Such a test apparatus is described, for example, in German Patent Application No. 103 41 836.9.
Testing mixed-signal semiconductor components frequently involves the use of function generators in order to generate reference signals. Function generators are electrical circuits whose output produces voltages or currents whose waveform has a desired shape and thus simulates a function. Typical functions which are simulated by function generators are square wave functions, sawtooth functions, noise and harmonic functions such as sine or cosine functions.
The reference signals provided by function generators in test apparatuses are either applied to the semiconductor components to be tested or are used as reference input signals for measuring apparatuses.
Particular demands are placed on these reference signals for testing mixed-signal semiconductor components. The metallurgy and measurement methods cause effects such as aliasing effects or phase noise, which produce errors in the measurement results. To eliminate said effects, the measurement results are averaged.
A sinusoidal reference signal therefore cannot be generated by function generators which generate just one period of the signal and then read this one period cyclically. In this case, the measurement results would merely be repeated and averaging would not eliminate said measurement errors. Rather, signals which are not obtained by merely repeating just one period need to be generated by the function generator for a plurality of periods. Sinusoidal functions are understood to mean sine and cosine functions in sine, cosine and linear combinations.
In the test apparatuses, long lines run from the function generators used to the semiconductor components which are to be tested or to the measuring apparatuses. These long lines impair the signal quality, which corrupts the measurement results. Possible sources of error are voltage drops on the lines and interference from radio-frequency radiation.